Kitabı oku: «A History of Inventions, Discoveries, and Origins, Volume I (of 2)», sayfa 32

ULTRAMARINE

Ultramarine is a very fine blue powder, almost of the colour of the corn-flower or blue-bottle, which has this uncommon property, that, when exposed to the air or a moderate heat, it neither fades nor becomes tarnished. On this account it is used in painting; but it was employed formerly for that purpose much more than at present, as smalt, a far cheaper article, was not then known. It is made of the blue parts of the lapis lazuli, by separating them as much as possible from the other coloured particles with which they are mixed, and reducing them to a fine powder. The real lapis lazuli is found in the mountains of that part of Tartary called Bucharia, which extends eastwards from the Caspian sea, and particularly at Kalab and Budukschu. It is sent thence to the East Indies, and from the East Indies to Europe. The Bucharians also carry fragments of it, weighing sometimes a pound and more, to Orenburg, though less frequently than some years ago. As large pieces of a pure and beautiful colour are scarce even in that distant country, and as they are employed for making ornaments and toys, the rough stone itself is costly; and this high price is increased in the ultramarine by its laborious preparation, though in later times the process has been rendered much easier¹⁴⁴³.

On account of the scarcity and great value of the lapis lazuli, other stones, somewhat like it only in colour, have been substituted in its stead; and hence have arisen the many contradictions to be found in the works of different authors, particularly those of the ancients, where they speak of the properties and country of this species of stone. Many have considered the Armenian stone, which is a calcareous kind of stone tinged with copper; many the mountain blue or malachite, and many also blue sparry fluor, and blue jasper, as the lapis lazuli¹⁴⁴⁴; and ultramarine of course is not always what it ought to be. At present, smalt of a good colour is often purchased therefore at a dear rate; and it is in greater request, as it is certain that its colour is more durable in fire than even that of the lapis lazuli. Good ultramarine must be of a beautiful dark colour, and free from sand as well as every other mixture. It must unite readily with oil; it must not become tarnished on a red-hot tile or plate of iron, and it ought to dissolve in strong acids, almost like the zeolite, without causing any effervescence. In the year 1763, an ounce of it at Paris cost four pounds sterling, and an ounce of cendre d’outremer, which is the refuse, two pounds. At Hamburg, Gleditsch sold fine real Oriental ultramarine for a ducat per ounce, and warranted it to stand proof by fire; but whether it would stand proof by acids also, I do not know.

From what has been said, a question arises, whether ultramarine was known to the ancient Greeks and Romans? And this gives occasion to another, whether they were acquainted with lapis lazuli? The name lapis lazuli no one indeed can expect to find among them; for it is certain that we received it from the Arabians; and the word ultramarinum is altogether barbarous Latin. Some centuries ago, many foreign articles, brought from beyond sea, had a name given them from that circumstance; and the ancients applied the epithet marinum to various productions on the like account. Hence, in the decline of the Roman language was formed ultramarinum, which some have endeavoured to improve by changing it into transmarinum, but this among the ancients never signified a colour.

Though the ancient names of precious stones have neither been examined with sufficient accuracy nor distinguished with the greatest possible certainty, I think I can discover among them the lapis lazuli. I consider it as the sapphire of the ancients, and this opinion has been entertained by others; but I hope to render it more probable than it has hitherto appeared. In the first place, the sapphire of the Greeks and Romans was of a sky-blue colour with a violet or purplish glance; and sometimes it had a very dark or almost blackish-blue colour. Secondly, this stone was not transparent. Thirdly, it had in it a great many gold points, or golden-yellow spots, but that which had fewest was most esteemed. Fourthly, it was polished and cut; but when it was not perfectly pure, and had mixed with it harder extraneous particles, it was not fit for the hands of the lapidary. Fifthly, it appears that it was procured in such large pieces that it could be employed for inlaid or mosaic-work. Sixthly, it was often confounded with, or compared to, copper-blue, copper-ore, and earth and stones impregnated with that metal. Seventhly, such medicinal effects were ascribed to it as could be possessed only by a copper salt; and lastly, it formed veins in rocks of other kinds of stone, as we are informed by Dionysius¹⁴⁴⁵.

That a stone with these properties cannot be the sapphire of our jewellers is beyond all doubt. Our real sapphire does not form veins in other fossils, but is found among sand in small crystals, shaped like diamonds; though they sometimes have rather the figure of columns. Like other precious stones, they are always transparent; they have never gold points in them; their blue colour resembles more or less that of blue velvet, and it is often very pale, and approaches seldom, or very little, to purple. Powder of sapphire appears like fine pounded glass, exhibits no traces of copper, and can in no manner produce a blue pigment, or be confounded with mountain-blue.

The question, whether the ancients were acquainted with our sapphire, and whether it may not belong to their amethysts or hyacinths, I shall not here examine. I am inclined rather to decide in the negative than the affirmative; and at any rate the proof will always remain dubious. It might perhaps be difficult also to determine whether every modern mineralogist who has spoken of the sapphire was acquainted with, and alluded to, the real stone of that name.

On the other hand, we can affirm with the greatest certainty, that the sapphire of the ancients was our lapis lazuli. The latter is of a blue colour, which inclines sometimes to violet or purple, and which is often very dark. It is altogether opake, yet its colour will admit of being compared to a sky-colour; in mentioning of which Pliny had no idea of transparency, for he compares the colour of an opake jasper to a sky-blue¹⁴⁴⁶. The lapis lazuli is interspersed with small points, which were formerly considered as gold, but which are only particles of pyrites or marcasite. It can be easily cut and formed into articles of various kinds, and at present it is often used for seals. Pliny, however, informs us that it was not fit for this purpose when it was mixed with hard foreign particles, such as quartz; and that which was of one colour was therefore much more esteemed¹⁴⁴⁷. Many cut stones of this kind, which are considered as antiques, may be found in collections. I remember to have seen several works of this sort in the excellent collection of the duke of Brunswick, which, in all probability, are Egyptian, and which are worthy of an accurate description. That lapis lazuli was used formerly for inlaid works I am well convinced, though at present I can produce no proofs. In how beautiful a manner it is employed for that purpose in Florentine works, is well known. The largest and most magnificent squares of lapis lazuli which I ever saw, are in the apartments at Zarskoe-Selo, a summer palace near Petersburg, belonging to the empress of Russia, the walls of which are covered with amber, interspersed with plates of this costly stone. I was informed that these plates were procured from Thibet. The doubt expressed by Epiphanius concerning stairs overlaid with lapis lazuli, respects only the great expense of it, and he perhaps imagined that the steps were entirely cut from the solid stone. The confounding the sapphire with the cyanus, or comparing it to it, of which several instances occur, proves that the former must have had a great resemblance to copper-ore; for that the cyanus is a kind of mineral or mountain blue, tinged with copper, I have proved already¹⁴⁴⁸. The blue colour of lapis lazuli has always been supposed to be owing to copper; but according to the latest discoveries it originates from iron¹⁴⁴⁹. The medicinal effects which the ancients ascribed to their sapphire could be produced only from a mixture of copper, as they considered the Armenian stone, or false lapis lazuli, to be the real kind. They recommended copper ochre for an inflammation of the eyes¹⁴⁵⁰. In the last place it agrees with what Dionysius says, that the sapphire or lapis lazuli was produced in veins among other kinds of stone¹⁴⁵¹. The sapphire also mentioned in the oldest writings of the Hebrews, appears to be no other than the sapphire of the Greeks, or our lapis lazuli; for it was said likewise to be interspersed with gold points¹⁴⁵².

The ancients therefore were acquainted with our lapis lazuli; but the question whether they used it as a paint, or prepared ultramarine from it, I cannot answer with sufficient certainty. It is possible that their cæruleum sometimes may have been real ultramarine; but properly and in general it was only copper ochre¹⁴⁵³. The objection that the ancients made blue glass and blue enamel, and if they had not smalt they could use no other pigment that would stand fire but ultramarine, I shall answer in the next article.

Before I proceed to the oldest information with which I am acquainted respecting ultramarine, or the blue colour made from lapis lazuli, I shall communicate what I know of the origin and antiquity of the name commonly given to this stone. That I might be able to offer something more on the subject than what has been said by Salmasius¹⁴⁵⁴, I requested the opinion of Professor Tychsen, which, with his permission, I have here subjoined¹⁴⁵⁵. It is, in the first place, certain that the word is of Persian derivation, and the stone, as I have already remarked, has hitherto been brought to us from Persia. Secondly, it signifies a blue colour. It was at first also the common name in Europe for blue stones and blue colours used in painting; and it was a long time used to express mountain-blue impregnated with copper. The modern systematic mineralogists, it appears, first appropriated the corrupted Persian word to the present lazur-stone, properly so-called; and those therefore would commit an error in mineralogy who should now apply this name to the Armenian stone, mountain-blue, or any other blue mineral containing copper.

Without pretending to have discovered the first mention of the name lazuli in those writings which have been handed down to us, I shall here offer, as the oldest with which I am acquainted, that found in Leontius¹⁴⁵⁶, who, where he gives directions for colouring a celestial globe, speaks of lazurium. If Fabricius be right, Leontius lived in the sixth century¹⁴⁵⁷. Among the receipts for painting, written in the eighth century, which Muratori¹⁴⁵⁸ has made known, we find an unintelligible account how to make lazuri, for which cyanus compositus, perhaps a prepared kind of mountain-blue, was to be employed. There is also another receipt which orders blue-bottles to be pounded in a mortar. It appears therefore that this word was used in the corrupted Latin of that period to signify a blue colour for painting. The same word, formed after the Greek manner, seems to have been used for blue by Achmet, the astrologer, who lived in the ninth century¹⁴⁵⁹, and by Nonus in the tenth for a blue earth¹⁴⁶⁰. Of still more importance is a passage of Arethas, who lived in the following century, and who, in his exposition of a verse in the book of Revelation¹⁴⁶¹, says, the sapphire is that stone, of which lazurium, as we are told, is made¹⁴⁶². This, therefore, is a strong corroboration that the sapphire of the ancients was our lapis lazuli, and appears to be the first certain mention of real ultramarine. The word however occurs often in the succeeding centuries for blue copper-ochre. Constantinus Africanus, a physician of the eleventh century, ascribes to lapis lazuli the same medicinal qualities as those of copper-ochre¹⁴⁶³; as do also Avicenna, Averroes, and Myrepsius. The first, under the letter lam, gives a chapter entitled lazuard, to which the translator has prefixed “De azulo, id est, de lapide Armenio;” and the last says expressly, that the lapis lazuli of the Latins is the lazurios of the Greeks¹⁴⁶⁴. The words azura, azurum, azurrum, occur often also in that century for blue.

The name ultramarine, or, as it was first called, azurrum ultramarinum, I have not yet found in any writer of the fifteenth century. But it appears that it must have been common about the end of that century, as it was used by Camillus Leonardus in 1502¹⁴⁶⁵. It is probable that it originated in Italy. In the first half of the sixteenth century Vanuccio Biringoccio gave directions for preparing the real ultramarine, which he distinguishes with sufficient accuracy from copper azur¹⁴⁶⁶, or, as he calls it, the azurro dell’ Alemagna. At that period, however, the best method of preparing it must have been doubtful as well as little known, and on that account of no great benefit; for, in the beginning of the sixteenth century, the father of the celebrated Giambatista Pigna, an apothecary at Modena, was in possession of the secret for making the best ultramarine, by which he acquired more riches than would have arisen from a large estate¹⁴⁶⁷. It is not, therefore, altogether true that Alexius Pedemontanus, as Spielmann relates¹⁴⁶⁸, was the first person who mentioned ultramarine. I am of opinion that this Alexius, or Hieronymus Ruscellai concealed under that name, who wrote in the beginning of the sixteenth century, only first published a complete account of the method of preparing it. At any rate, his receipt was long followed as the best and the most certain¹⁴⁶⁹. But on what information is that assertion founded, which we read in English and French authors¹⁴⁷⁰, that the preparation of ultramarine was found out in England, and that a servant of the East India Company disclosed it, in order to be revenged for some injury which he had sustained?

[The following is the method of making ultramarine from lapis lazuli. The finest mineral is selected, heated to a dull red heat, and quenched in water; it is thus rendered friable, and is ground down into an impalpable powder. This is then mixed with a tenacious paste made of linseed oil, wax, resin, turpentine and mastic; and the mixture being kneaded in warm water gives out the blue particles, which are afterwards collected by subsidence.

Chemists are not agreed concerning the cause of the colour of ultramarine. Dr. Eisner considers it to arise from sulphuret of sodium and of iron, the former being a higher sulphuret than the latter. MM. Clement and Desormes show that the iron is not essential, either to the lapis lazuli, or to the pigment made from it.

An artificial method of making ultramarine was discovered in 1828 by M. Guimet; the process has been kept secret. Processes have also been discovered by M. Gmelin of Tübingen, M. Persoz of Strasburg, and others. M. Gmelin’s process consists in fusing a mixture of two parts of sulphur and one of dry carbonate of soda in a Hessian crucible, and then sprinkling into it by degrees another mixture of silicate of soda and aluminate of soda. The crucible must be exposed to the fire for an hour after this. The ultramarine thus prepared contains a little sulphur, which can be separated by means of water.

Some valuable observations on this subject have lately been published by M. Prückner¹⁴⁷¹. He states that the materials required in the preparation of ultramarine are alumina, sulphate of soda, sulphur, charcoal and a salt of iron, the common sulphate or green vitriol being the best. The alumina is supplied in white bole, or a very pure white clay. The sulphate of soda is reduced by charcoal and heat to the state of sulphuret, and its solution thus obtained afterwards boiled with sulphur so as to form a persulphuret (penta-sulphuret, Berz.). The solution is then mixed with the dried clay and stirred; during the mixing a solution of green vitriol is added and mixed. It is then dried and very finely powdered as rapidly as possible. It is afterwards heated in a muffle; then washed, drained and again heated in a muffle; finally it is again washed, dried and powdered.]

COBALT, ZAFFER, SMALT

The name cobalt is given at present to that metal and its ores, the oxides of which are largely employed in the manufactures of glass, porcelain and pottery, for the production of a blue colour. The cobalt ores are first roasted and freed from foreign mineral bodies, particularly sulphur, iron, nickel, bismuth, and arsenic, with which they are united, and then well calcined, and sold, either mixed or unmixed with fine sand, under the name of zaffer (zaffera); or the cobalt is melted with siliceous earth and potash to a kind of blue glass called smalt, which, when ground very fine, is known in commerce by the name of powder-blue. All these articles, because they are most durable pigments, and those which best withstand fire, and because one can produce with them every shade of blue, are employed, above all, for tinging crystal and for enamelling; for counterfeiting opake and transparent precious stones, and for painting and varnishing real porcelain and earthen and potters’ ware. This colour is indispensably necessary to the painter when he is desirous of imitating the fine azure colour of many butterflies and other natural objects; and the cheaper kind is employed to give a blueish tinge to new-washed linen, which so readily changes to a disagreeable yellow.

The preparation of this new colour may be reckoned among the most beneficial inventions of modern times. It rendered of importance an useless and hurtful production; gave employment to a number of hands; assisted in bringing many arts to a degree of perfection which they could never before attain; and has drawn back to Germany a great deal of money which was formerly sent out of it for foreign articles.

Though there is no doubt that the process used in the preparation of cobalt and smalt was invented about the end of the fifteenth or the beginning of the sixteenth century, we have reason to ask whether the ancients were acquainted with cobalt, and if they employed it for colouring glass. They opened and worked mines in various parts; and it is at any rate possible that they may have found cobalt; they made many successful attempts to give different tints to glass¹⁴⁷²; and they produced blue glass and blue enamel. They may have learned by an accident to make this glass, as they did to make brass; and they may have continued to make the former as long as their supply of coloured earth lasted. When the mineral failed them, they may have lost the art, in the same manner as the method of preparing Corinthian brass¹⁴⁷³ was lost for a considerable space of time. The use of cobalt does not imply a knowledge of its metal; for the moderns made brass and smalt for whole centuries, before they learned to prepare zinc and regulus of cobalt.

It seems, however, difficult to answer this question; for one can scarcely hope to discover cobalt with any certainty among those minerals mentioned by the ancients. They could describe minerals in no other manner than according to their exterior appearance, the country where they were found, or the use to which they applied them. Now there is no species more various and more changeable in its figure and colour than cobalt ore, which on this account shows the impossibility of distinguishing minerals with sufficient accuracy by external characteristics. Besides, there are scarcely two passages of the ancients which seem to allude to it; and these, when closely examined, give us little or no information.

The meaning of the term cadmia is as various and uncertain as that of the word cobalt was two centuries ago. It signified often calamine; sometimes furnace-dross; and perhaps, in later times, also arsenic; but, as far as I know, it was never applied to cobalt till mineralogists wished in modern times to find a Latin term for it¹⁴⁷⁴, and assumed that which did not belong properly to any other mineral. The well-known passage of Pliny¹⁴⁷⁵, in which Lehmann thinks he can with certainty distinguish cobalt, is so singular a medley that nothing to be depended on can be gathered from it. The author, it is true, where he treats of mineral pigments, seems to speak of a blue sand which produced different shades of blue paint, according as it was pounded coarser or finer. The palest powder was called lomentum; and this Lehmann considers as our powder-blue. I am however fully convinced that the cyanus of Theophrastus, the cæruleum of Pliny, and the chrysocolla¹⁴⁷⁶, were the blue copper earth often already mentioned, which may have been mixed and blended together. Besides, Pliny clearly adds to it an artificial colour, which in my opinion was made in the same manner as our lake; for he speaks of an earth, which when boiled with plants, acquired their blue colour, and which was in some measure inflammable. With these pigments walls were painted; but as many of them would not endure lime, they could be used only on those which were plastered with clay (creta). The expression usus ad fenestras has been misapplied by Lehmann, as a strong proof of his assertion; for he explains it as if Pliny had said that a blue pigment was used for painting window-frames; but glass windows were at that time unknown. I suspect Pliny meant to say only that one kind of paint could not be employed near openings which afforded a passage to the light, as it soon decayed and lost its colour. This would have been the case in particular with lake in which there was a mixture of vegetable particles.

For my part, I find in this passage as few traces of smalt as M. Gmelin; and I agree with him in opinion that the strong and unpleasant mixtures arising from cobalt would, had it been known, have induced the ancients to make particular mention of it in their writings. Would not the arsenic, which is so often combined with cobalt, have given occasion to many reports respecting the dangerous properties of these minerals? And would not arsenic and bismuth have been sooner known, had preparations of cobalt been made at so early a period? It is a circumstance of great weight also, that in the places where the ancients had mines, and where antiquities painted or tinged blue, and resembling in colour that produced by cobalt, have been dug up, cobalt has not been discovered, or has been discovered only in modern times. At present we know nothing of Egyptian, Arabian, Ethiopian, Italian, and Cyprian cobalt; and in Spain¹⁴⁷⁷ this mineral was first found in the reign of Philip IV. I shall here observe, that the island of Cyprus was formerly so abundant in copper, that, in a mineralogical sense, it might be called the island of Venus; and we can therefore entertain the less doubt that the cæruleum Cyprium was copper-blue.

The principal reason, however, why Lehmann, Pauw¹⁴⁷⁸, Ferber, Delaval, and others, think that the ancients used smalt, and were acquainted with cobalt, is that, as has been already said, various antiquities both of painting and enamel have been discovered, in which a blue appears that seems to give grounds for conjecturing that it was produced by cobalt. Ferber¹⁴⁷⁹ speaks of blue glass squares in mosaic-work; and Delaval mentions old Egyptian glass-work of this colour¹⁴⁸⁰. It is well known also that the Chinese and people of Japan gave to their porcelain that fine blue colour, for which it is celebrated, long before the discovery of smalt in Europe. On mummies a blue is seen likewise, which, even after so many centuries, seems to have lost little or nothing of its beauty¹⁴⁸¹. We must therefore allow that the ancients used either ultramarine or cobalt.

The first opinion seems, in regard of porcelain, to be confirmed by Duhalde¹⁴⁸², who speaks of a mine of azur, and relates that the Chinese, in modern times, use instead of it, for painting their porcelain, a blue colour brought from foreign countries. It is probable that by the former he means lapis lazuli, and by the latter smalt, which is sent in large quantities from Europe to China. The invention of ultramarine, however, appears to me too new, its effect on porcelain too uncertain, and its price too high to allow us to suppose that it has been much used. We should therefore have been almost obliged to adopt the latter opinion, had not M. Gmelin proved by chemical experiments¹⁴⁸³ that it is not only possible to give to glass and enamel a blue colour by means of iron, but that the before-mentioned antiquities, upon which so much stress has been laid, show not the smallest traces of cobalt. He even made experiments upon blue tiles, found in a Roman tessellated foot-pavement at Montbeillard; and likewise on the blue paint of the mummy which was presented to our university by the king of Denmark¹⁴⁸⁴. He has also mentioned various articles on which a blue colour is produced by the vitrification of iron. Of this nature are in particular those slags found near the smelting-houses at the iron-mines of the Harz forest; and I myself have seen slags which were of a blue colour exceedingly beautiful. Volcanic slags, or scoriæ, found in the neighbourhood of Verona, Vicenza, and other parts of Italy, are mentioned also by Ferber¹⁴⁸⁵, which seems to confirm the conjecture of Dr. Bruckmann¹⁴⁸⁶, that the ancients may have used such slags for their works. It is probable that the ancients were first induced by the blue slag of their smelting-houses to make experiments on the colouring of glass with iron, and that in this art they acquired a dexterity not possessed at present, because it was abandoned by our ancestors after the invention of smalt, which is much more beautiful; and which can be used more easily and with more certainty. I cannot, however, deny that I have often lamented this loss when I saw the excellent blue in the painted windows at Gouda, Goslar, and other places; though its beauty is much heightened by the transparency of the glass, and the strong light that falls upon it from without.

I shall now proceed to the invention of the colour prepared from cobalt. About the end of the fifteenth century, cobalt appears to have been dug up in great quantity in the mines on the borders of Saxony and Bohemia, discovered not long before that period. As it was not known at first to what purpose it could be applied, it was thrown aside as a useless mineral. The miners had an aversion to it, not only because it gave them much fruitless labour, but because it often proved prejudicial to their health by the arsenical particles with which it was combined; and it appears even that the mineralogical name cobalt then first took its rise. At any rate, I have never met with it before the beginning of the sixteenth century; and Mathesius and Agricola seem to have first used it in their writings. Frisch derives it from the Bohemian word kow, which signifies metal; but the conjecture that it was formed from cobalus, which was the name of a spirit that, according to the superstitious notions of the times, haunted mines, destroyed the labours of the miners, and often gave them a great deal of unnecessary trouble, is more probable; and there is reason to think that the latter is borrowed from the Greek. The miners, perhaps, gave this name to the mineral out of joke, because it thwarted them as much as the supposed spirit, by exciting false hopes and rendering their labour often fruitless¹⁴⁸⁷. It was once customary, therefore, to introduce into the church service a prayer that God would preserve miners and their works from kobolts and spirits.

Respecting the invention of making a useful kind of blue glass from cobalt, we have no better information than that which Klotzsch¹⁴⁸⁸ has published from the papers of Christian Lehmann. The former, author of an historical work respecting the upper district of the mines in Misnia, and a clergyman at Scheibenberg, collected with great diligence every information in regard to the history of the neighbouring country, and died, at a great age, in 1688. According to his account, the colour-mills, at the time when he wrote, were about a hundred years old; and as he began first to write towards the end of the thirty years’ war, the invention seems to fall about 1540 or 1560. He relates the circumstance as follows: “Christopher Schurer, a glass-maker at Platten, a place which belongs still to Bohemia, retired to Neudeck, where he established his business. Being once at Schneeberg, he collected some of the beautiful coloured pieces of cobalt which were found there, tried them in his furnace; and finding that they melted, he mixed some cobalt with the vitreous mass, and obtained fine blue glass. At first he prepared it only for the use of the potters; but in the course of time it was carried as an article of merchandize to Nuremberg, and thence to Holland. As painting on glass was then much cultivated in the latter, the artists there knew better how to appreciate this invention. Some Dutchmen therefore repaired to Neudeck, in order that they might learn the process used in preparing this new colour. By great promises they persuaded the inventor to remove to Magdeburg, where he also made glass from the cobalt of Schneeberg; but he again returned to his former residence, where he constructed a hand-mill to grind his glass, and afterwards erected one driven by water. At that period the colour was worth seven dollars and a half per cwt., and in Holland from fifty to sixty florins. Eight colour-mills of the same kind, for which roasted cobalt was procured in casks from Schneeberg, were soon constructed in Holland; and it appears that the Dutch must have been much better acquainted with the art of preparing, and particularly with that of grinding it, than the Saxons; for the elector John George sent for two colour-makers from Holland, and gave a thousand florins towards enabling them to improve the art. He was induced to make this advance chiefly by a remark of the people of Schneeberg, that the part of the cobalt which dropped down while it was roasting contained more colour than the roasted cobalt itself. In a little time other colour-mills were erected around Schneeberg. Hans Burghard, a merchant and chamberlain of Schneeberg, built one by which the eleven mills at Platten were much injured. Paul Nordhoff, a Frieslander, a man of great ingenuity, who lived at the Zwitter-mill, made a great many experiments in order to improve the colour, by which he was reduced to so much poverty that he was at length forced to abandon that place, where he had been employed for ten years in the colour-manufactory. He retired to Annaberg, established there in 1649, by the assistance of a merchant at Leipsic, a colour-manufactory, of which he was appointed the director; and by these means rendered the Annaberg cobalt of utility. The consumption of this article however must have decreased in the course of time; for in the year 1659, when there were mills of the same kind at more of the towns in the neighbourhood of mines, he had on hand above 8000 quintals.” Thus far Lehmann.